scholarly journals Active Transport of Inorganic Carbon Increases the Rate of O2 Photoreduction by the Cyanobacterium Synechococcus UTEX 625

1988 ◽  
Vol 88 (1) ◽  
pp. 6-9 ◽  
Author(s):  
Anthony G. Miller ◽  
George S. Espie ◽  
David T. Canvin
Keyword(s):  
Active Transport ◽  
Inorganic Carbon

Physiological aspects of CO2 and HCO3− transport by cyanobacteria: a review

1990 ◽  
Vol 68 (6) ◽  
pp. 1291-1302 ◽  
Author(s):  
Anthony G. Miller ◽  
George S. Espie ◽  
David T. Canvin
Keyword(s):  
Active Transport ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Structural Analog ◽  
Transport Systems ◽  
Ribulose Bisphosphate Carboxylase ◽  
High Concentration ◽  
Bisphosphate Carboxylase ◽  
Ribulose Bisphosphate Carboxylase Oxygenase ◽  
Inorganic Carbon Transport

Cyanobacteria grown at air levels of CO2, or lower, have a very high photosynthetic affinity for CO2. For ceils grown in carbon-limited chemostats at pH 9.6, the K0.5 (CO2) for whole cell CO2 fixation is about 3 nM. This is in spite of a K0.5 (CO2) for cyanobacterial ribulose bisphosphate carboxylase/oxygenase of about 200 μM. It is now clear that cyanobacteria can photosynthesize at very low CO2 concentrations because they raise the CO2 concentration dramatically around the carboxylase. This rise in the intracellular CO2 concentration involves the active transport of HCO3− and CO2, perhaps by separate transport systems. The transport of HCO3− often requires millimolar levels of Na+, and this provides a ready means of initiating HCO3− transport. The active transport of CO2 requires only micromolar levels of Na+. In the rather dense cell suspensions used in transport studies the extent of CO2 uptake is often limited by the rate at which CO2 can be formed from the HCO3− in the medium. The addition of carbonic anhydrase relieves this kinetic limitation on CO2 transport. The active transport of CO2 can be selectively inhibited by the structural analog carbon oxysulfide (COS). When HCO3− transport is allowed in the presence of COS there is a substantial net leakage of CO2 from the cells. This leaked CO2 results from the intracellular dehydration of the accumulated HCO3−. This CO2 is normally scavenged by the active CO2 pump. If cells are allowed to transport H13C18O18O18O− for 5 s and if CO2 transport is suddenly quenched by the addition of COS, then a rapid leakage of 13C16O16O occurs. If the rapidly released CO2 was actually present in the cells before the addition of the COS, then the intracellular CO2 concentration would have been about 0.6 mM. Not only is this a high concentration, but since the leaked CO2 was completely depleted of the initial 18O, it must have been in rapid equilibrium with the total dissolved inorganic carbon within the cells. Cells grown on high levels of inorganic carbon, either as CO2 or HCO3−, lack the active HCO3− system but still retain a capacity, albeit reduced, for CO2 transport. Cyanobacteria seem to adjust their complement of inorganic carbon transport systems so that the K0.5 for transport is close to the inorganic carbon concentration of the growth medium.

Inorganic carbon acquisition and its energization in eustigmatophyte algae

2002 ◽  
Vol 29 (3) ◽  
pp. 271 ◽  
Author(s):  
I. Emma Huertas ◽  
Brian Colman ◽  
George S. Espie
Keyword(s):  
Active Transport ◽  
Co2 Fixation ◽  
Inorganic Carbon ◽  
Mitochondrial Activity ◽  
Nannochloropsis Gaditana ◽  
Unicellular Algae ◽  
Basal Group ◽  
Intracellular Ca ◽  
Active Transport Process ◽  
Monodus Subterraneus

The eustigmatophyceans are primitive unicellular algae that represent the most basal group of ochrophytes. They are believed to be obligate photoautotrophs, occurring mainly in freshwater and soil but with some marine representatives. The freshwater eustigmatophytes Monodus subterraneus and Vischeria stellata, and the marine eustigmatophyte Nannochloropsis gaditana, have been studied by mass spectrometry with respect to their characteristics for inorganic carbon (Ci) uptake. A CO2 concentrating mechanism was found in all three, but an external carbonic anhydrase (CA) was not detected. The acquisition of Ci from the external medium was based on the active transport of HCO3–, CO2, or both. In particular, N. gaditana was able to use HCO3– exclusively as an exogenous carbon source for photosynthesis, with this HCO3– being subsequently converted to CO2 by an intracellular CA for photosynthetic fixation. A unique characteristic of this species was its capacity to transport HCO3– during prolonged periods of time in the dark. In contrast, M. subterraneus utilized CO2 alone through an active transport process, whereas V. stellataexhibited the capacity to transport both HCO3– and CO2. The uptake of CO2 also continued in the dark in V. stellatacells. Regardless of the Ci species taken up, transport was abolished by anoxia and by inhibitors of mitochondrial respiration. These results indicate that that the supply of Ci for photosynthetic CO2 fixation is partly dependent upon mitochondrial activity in these primitive eukaryotes.

Active transport of inorganic carbon into cells of blue-green algae (Cyanophyta)

2002 ◽  
Vol 4 (4) ◽  
pp. 29-40
Author(s):  
A. F. Tereshchenko ◽  
V. V. Podorvanov ◽  
E. K. Zolotareva
Keyword(s):  
Active Transport ◽  
Green Algae ◽  
Inorganic Carbon ◽  
Blue Green Algae

Zooplankton vertical migration and the active transport of dissolved organic and inorganic carbon in the Sargasso Sea

2000 ◽  
Vol 47 (1) ◽  
pp. 137-158 ◽  
Author(s):  
Deborah K. Steinberg ◽  
Craig A. Carlson ◽  
Nicholas R. Bates ◽  
Sarah A. Goldthwait ◽  
Laurence P. Madin ◽  
...  
Keyword(s):  
Active Transport ◽  
Vertical Migration ◽  
Inorganic Carbon ◽  
Sargasso Sea ◽  
Organic And Inorganic Carbon

The diversity of inorganic carbon acquisition mechanisms in eukaryotic microalgae

2002 ◽  
Vol 29 (3) ◽  
pp. 261 ◽  
Author(s):  
Brian Colman ◽  
I. Emma Huertas ◽  
Shabana Bhatti ◽  
Jeffrey S. Dason
Keyword(s):  
Active Transport ◽  
Active Site ◽  
Inorganic Carbon ◽  
Algal Species ◽  
Isochrysis Galbana ◽  
Co2 Uptake ◽  
Ecological Distribution ◽  
Aquatic Medium ◽  
Low Co2 ◽  
Marine Dinoflagellates

Eukaryotic microalgae have developed CO2concentrating mechanisms to maximise the concentration of CO2 at the active site of Rubisco in response to the low CO2 concentrations in the external aquatic medium. In these organisms, the modes of inorganic carbon (Ci) uptake are diverse, ranging from diffusive CO2 uptake to the active transport of HCO3 -and CO2 and many have an external carbonic anhydrase to facilitate HCO3- use. There is unequivocal evidence for the mechanisms of Ci uptake in only about 25 species of microalgae of the chlorophyte, haptophyte, rhodophyte, diatom, and eustigmatophyte groups. Most of these species take up both CO2 and HCO3-, but the rates of uptake of each of these substrates varies with the algal species. A few species take up only one of the two forms of Ci, an adaptation that is not necessarily correlated with their ecological distribution. Evidence is presented for the active uptake of HCO3- and CO2 in two marine haptophytes,Isochrysis galbana Parke and Dicrateria inornata Parke, and for active transport of CO2 but lack of HCO3- uptake in two marine dinoflagellates, Amphidinium carteraeHulburt and Heterocapsa oceanica Stein.

Diffusion and Active Transport of Inorganic Carbon Species in Freshwater and Marine Macroalgae

1987 ◽  
pp. 333-340 ◽  
Author(s):  
John A. Raven ◽  
Andrew M. Johnston ◽  
Jeffrey J. MacFarlane ◽  
Misni Bin Surif ◽  
Shona McInory
Keyword(s):  
Active Transport ◽  
Inorganic Carbon ◽  
Marine Macroalgae ◽  
Carbon Species

Na+-dependent HCO3-transport in the cyanobacteriumSynechocystisPCC6803

1998 ◽  
Vol 76 (6) ◽  
pp. 1084-1091 ◽  
Author(s):  
Anthony KC So ◽  
Aleem Kassam ◽  
George S Espie
Keyword(s):  
Active Transport ◽  
Maximum Rate ◽  
Inorganic Carbon ◽  
Ph Regulation ◽  
Electrochemical Potential ◽  
Unicellular Cyanobacterium ◽  
Intracellular Ph Regulation ◽  
Synechocystis Pcc6803 ◽  
Accumulation Kinetic ◽  
Centrifugation Technique

The effect of Na+on HCO3-transport, inorganic carbon (Ci) accumulation, and photosynthesis was investigated in the unicellular cyanobacterium Synechocystis sp. PCC6803 using the silicone fluid filtering centrifugation technique. Unlike other cyanobacteria, Synechocystis cells grown at low Ciin standing culture had little capacity for Na+-independent HCO3-transport, when assayed at pH 9.6. However, 25 mM NaCl, but not KCl, strongly promoted HCO3-transport and accumulation. Kinetic analysis indicated that the HCO3-concentration required for one half the maximum rate of transport, K0.5(HCO3-), decreased in the presence of Na+while the maximum rate of transport, VMAX, increased by up to 15-fold. Na+-dependent HCO3-transport occurred against an electrochemical potential of up to 24 kJ ·mol-1, indicating the involvement of carrier-mediated active transport. Li+(1-3 mM) partially substituted for Na+in that K0.5( HCO3-) values were similar (38 vs. 50 µM), but VMAXwas reduced by twofold. At higher concentrations, Li+counteracted the effects of Na+. Monensin reversibly inhibited Na+-dependent HCO3-transport and acted by reducing VMAXwithout affecting K0.5(HCO3-). Monensin inhibition suggested that the electrochemical potential for Na+may play a role in Na+-dependent HCO3-transport, possibly through an involvement in intracellular pH regulation during transport. Na+also stimulated photosynthetic C fixation and O2evolution and these effects were correlated with the Na+-dependent increase in intracellular Ciaccumulation. The Na+-requirement for photosynthesis could be relieved by the provision of CA to the cell suspension, in agreement with the proposal that Na+is required for transport and not directly involved in the photosynthetic process.Key words: active transport, CO2-concentrating mechanism, cyanobacteria, Na+-dependent HCO3-transport, photosynthesis, Synechocystis PCC6803.

On the structural organization of biological pumps and channels

1984 ◽  
Vol 42 ◽  
pp. 138-141
Author(s):  
G. Zampighi ◽  
M. Kreman
Keyword(s):  
Active Transport ◽  
Transport System ◽  
Plasma Membranes ◽  
Transport Proteins ◽  
Molecular Organization ◽  
Passive Transport ◽  
Concentration Gradients ◽  
Cell Functions ◽  
Natural Concentration ◽  
Active Transport System

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

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